Stable aqueous emulsions

ABSTRACT

1. An emulsion copolymerization process for producing an aqueous emulsion comprising copolymerization of approximately by weight 1-99 parts of an N-vinyl lactam and 99 to 1 parts of a vinyl ester having the formula WHEREIN R is C1 18 alkyl, in an aqueous medium having a total solids content by weight of about 40 to 60% and containing as seeding agent 5-20% polymeric N-vinyl lactam based on the amount of said N-vinyl lactam.

United States Patent Barabas et al.

[$4] STABLE AQUEOUS EMULSIONS [72] Inventors: Eugene S. Barabas,Watchung; Marvin M. Fein, Westfield, both of NJ.

[73] Assignee: GAF Corporation, New York,

[22] Filed: May 4, 1970 [21] Appl. No.: 34,570

[52] US. Cl. .260/29.6 WB, 260/296 RW, 260/857,

260/875, 260/895 [51] lint. Cl ..C08f l/l3, C08f 19/00 [58] Field ofSearch ..260/29.6 RW, 29.6 WB, 875

[56] References Cited UNITED STATES PATENTS 2,890,199 6/1959 McNulty etal ..260/45.5 3,053,801 9/1962 Bingham et a1 ..260/45.5 3,402,987 9/1968Dalton et a1 ..8/31 3,488,312 1/1970 Barabas et a1. ..260/29.6 3,244,6584/1966 Grosser et a1 ..260/29.6

[ 51 Sept. 12, 1972 Primary Examiner-William H. Short AssistantExaminer-E. Nielsen Attorney-Samson B. Leavitt, Stephen J. Baron andWalter C. Kehm EXEMPLARY CLAIM 1. An emulsion copolymerization processfor producing an aqueous emulsion comprising copolymerization ofapproximately by weight 1-99 parts of an N-vinyl lactarn and 99 to 1parts of a vinyl ester having the formula wherein R is C alkyl, in anaqueous medium having a total solids content by weight of about 40 to60% and containing as seeding agent 5-20% polymeric N- vinyl lactambased on the amount of said N-vinyl lactam.

7 Claims, No Drawings STABLE AQUEOUS EMULSIONS The present inventionrelates in general to stable aqueous emulsions and more particularly tostable aqueous emulsions comprising copolymers of N-vinyl lactams andvinyl esters and a process for the preparation of such copolymers.

Film forming emulsion compositions comprising copolymers of N-vinyllactams and vinyl esters are well known in the art. These products aregenerally prepared either in bulk or in organic solvents or in aqueousdispersions, the latter procedure, of course, resulting in emulsionproducts. These emulsion processes are well known and generally comprisereacting the vinyl esters and the N-vinyl lactams in an aqueous solutionin the presence of an emulsifying or dispersing agent to produceemulsions or latices of the copolymers. V

The interpolymer .products which have been produced by these priorprocesses, while exhibiting utility as cast films or as film formingemulsion compositions, have yet to achieve significant value as theproperties of .the resultantcopolymerproducts tend to wherein Rrepresents an alkylene bridge necessary to fluctuate over a wide area.One of the most significant defects of these copolymers has beenthat'the viscosity of the products is subject 'to wide variances whereconsistency is often at a premium; This of course renders film castingemploying such products of dubious utility as the properties of thecopolymerproduct cannot be safely predicted.

It is clear therefore that 'a need has long existed in the art for aprocess which could produce copolymers of N- vinyl lactams and vinylesters, wherein the polymeric products exhibit controlled viscosities.

It'is accordingly one object of the present invention to provide a novelprocess for the production of novel copolymers of N-vinyl lactams andvinyl esters.

It is a further object of the present invention to provide a novelprocess for the production of copolymers of N-vinyl lactams and vinylesters which products exhibit controlled viscosities not knownheretofore in the art.

A still further object of the invention isto provide a new and improvedprocess for the production .of copolymers of N-vinyl lactams and vinylesters whereby the products produced by the process are capable ofexhibiting consistent viscosity values and therefore form cast films ofuniform properties.

Still other objects and advantages of the present invention will becomefurther apparent as the description thereof proceeds.

In accordance with the above defined objects and advantages, methodshave been devised according to this invention whereby stable aqueousemulsions or latices comprising copolymers of N-vinyllactams and vinylesters are produced which emulsion products show complete a'five, six orseven membered heterocyclic ring system and R represents a memberselected from the group consisting of hydrogen, alkyl, aryl, alkaryl andaralkyl groups. Each of these specific N-vinyl lactams characterized bythe foregoing general formula is commercially available.

Of the N-vinyl lactams described hereinabove, the preferred materialfor'use in forming the copolymers of this invention comprisesN'-vinyl-2-pyrrolidone and 5- methyl-N-vinyl-2-pyrrolidone.

The vinyl esters employed as starting materials in the process of thisinvention are those of the following general structural formula: g

wherein R is an alkyl group containing about one to 18 carbon atoms andpreferably containing one to seven carbon atoms. A preferred reactantmaterial falling within this group is vinyl acetate.

As pointed out hereinabove, the starting materials are copolymerized inthe presence of a polymeric N- vinyl lactam preferably one correspondingto the particular monomeric N-vinyl lactam chosen as one of the primarystarting materials. These polymeric products may be characterized by thefollowing general formula:

III.

Rr-CI-I C=O I/ T CH0Hz -jn wherein R represents an alkylene bridge groupnecessary to complete a 5-, 6- or 7-membered heterocyclic ring system,R, represents a member selected from the group consisting of hydrogen,alkyl, aryl, alkaryl and aralkyl groups, preferably hydrogen, and nrepresents a number indicative of the extent of polymerization. All ofthe specific polymeric materials characterized by the foregoing generalFormula III are commercially available and are called polymeric N-vinyllactams. In accordance with the preferred monomeric lactams, thepreferred polymer for use in the process is poly-N-vinyI-Z-pyrrolidone.

These polymeric materials may be obtained by polymerizing the monomericN-vinyllactams identified hereinabove in Formula I such as for example,N-vinyl- 2-pyrrolidone or N-vinyl-5-methyl-2-pyrrolidone and the like.Depending upon the extent of polymerization, these materials havemolecular weights ranging from at least 400 up to 2,000,000 or more. Inactual practice, a

mixture of polymeric molecules each containing a different number (n) ofmonomer units is always produced in forming the polymers.

According to the method of this invention, it has been found thatcopolymerization of a mixture of the aforesaid monomers in the presenceof a polymeric N- vinyl lactam results in the formation of copolymericproducts having novel and unexpected properties. According to theinvention it is essential that the polymeric N-vinyl lactam material bepresent at the seeding stage of the polymerization as this technique isbelieved to change the ordinary mechanism of the copolymerizationreaction. While not wishing to be bound by any particular theory ormechanism of reaction, it is believed that with the polymeric N-vinyllactam present at the seeding stage of polymerization, the reactionstarts on the surface of the polymer and the newly developed chains growinto the water phase thereof. This is in contradistinction to prioremulsion copolymerizations of vinyl esters and N-vinyl lactams carriedout by conventional methods wherein both the initiation and thepropagation steps take place in the organic phase. Thus, the productsproduced by the process of the invention are believed to constitute anarrangement of the polymer units not known heretofore.

The polymers produced in the process of the invention are obtained inthe form of emulsions of dispersion which have controlled or consistentviscosities. This controlled viscosity is present as different batchesof the copolymers are produced and constitutes a distinct improvementover products produced heretofore by conventional methods wherein theproduct viscosities are subject to wide variations.

As pointed out hereinabove the reaction is carried out in the presenceof a free radical initiator. These initiators or catalysts are wellknown in the art and generally comprise systems which yield freeradicals under the conditions of the reaction. For example, suchcompounds as organic and inorganic peroxides may be employed as it hasbeen found that such products yield free radicals under the conditionsemployed in the reaction. These materials include, for example, benzoylperoxide, cumene hydroperoxide, hydrogen peroxide, acetyl peroxide,lauroyl peroxide, persulfates such as alkali metal persulfates,including sodium and potassium persulfates. Also included are perboratessuch as sodium, potassium and ammonium perborate as well as a class ofcompounds referred to as azobisnitriles which may be represented byazobis-isobutyronitrile. If desired mixtures of these catalysts can beemployed. The preferred catalyst for conducting the reaction isazobis-isobutyronitrile, the latter compound referred to above.

The catalyst concentration employed in the reaction system is notnecessarily a critical feature of the invention as the amount thereofcan be varied over a wide range but advantageously an amount of catalystvarying from about 0.01 to 2.0 weight percent or more is preferablyemployed based on the total weight of the reactants being polymerized.

The temperature at which the invention is advantageously carried out canbe varied over a range of from about 75 C. to about 95 C. However, it ispreferred to conduct the polymerization reaction at a temperaturebetween about to C. to provide products having the desirable physicalcharacteristics of latex viscosity and molecular weight.

The polymerization reaction is preferably carried out in the absence offree oxygen as it has been found that the presence of free oxygen isdetrimental to the process of the invention. Also, it has been found tobe advantageous to conduct the process under a blanket of an inert gassuch as nitrogen, argon and the like.

In general the reactants may be employed in the polymerization processin any ratio desired, as the amount of each material employed will ofcourse serve to determine the constitution and properties of the finallyobtained polymeric product. It is preferred, however, to employ about 1to 99 parts by weight of the polymeric N-vinyl lactam to about 99 to 1parts by weight of the monomeric N-vinyl lactam with a correspondingamount of the vinyl ester. It is, of course, obvious that these amountsmay be varied depending on the properties of the desired polymer to beproduced.

The polymerization is carried out preferably by agitating the emulsioncontaining the reactants at the specified temperatures for a timesufficient for a predominant amount of the monomeric material to beconverted into resinous polymers. The process generally requires about 6to 12 hours, although this period will vary depending upon the startingmaterials and the specific conditions of the process.

If desired additional materials may be added to the reaction mixtureincluding activating agents such as alkali metal sulfites or bisulfitesin about the same amounts as the polymerization catalyst or initiator,in which case lower polymerization temperatures may be used. Also, it iswithin the scope of the invention to employ chain regulators such ashexyl, cetyl, dodecyl, etc., mercaptans in the polymerization reaction.Moreover, suitable surface active agents such as fatty acid soaps andfatty alcohol sulfates may be employed in the reaction.

The products obtained as a result of the polymerization reaction, whenproceeding in the manner described hereinbefore, are in the form offluid milkwhite, latex-like dispersions and exhibit controlled viscositywhen cast upon a substrate.

The emulsion can be compounded with additives such as pigments, salts,wetting agents, resins, waxes and the like, thus providing a widespectrum of products having varied industrial applications.

The following examples will serve to illustrate the practice of theinvention.

EXAMPLE 1 The apparatus employed for carrying out this example compriseda one-liter resin kettle equipped with mechanical stirrer, refluxcondenser, dropping funnel, gas inlet tube and thermometer.

339.5 Parts of distilled water was charged to the flask, and 5 parts ofpoly-N-vinyl-2-pyrrolidone (K-30) was added thereto and the mixturestirred until a clear solution was obtained. Thereafter a mixture of128.5 parts of vinyl acetate and 93.7 parts of N-vinyl-2-pyrrolidone wasadded in one batch. The system was then purged with nitrogen gasthoroughly and heated to 65 C. Then 0.345 parts azobis-isobutyronitrilewas inazobis-isobutyronitrile was added and the temperature was raisedto 80 to 85 C. in order to maintain the reflux of the mixture. Thistemperature range was maintained for two more hours whereupon anadditional 0.138 parts of azobis-isobutyronitrile was added and thereaction was continued until all the monomers were consumed. Thereafter,the mixture was cooled to room temperature and the resultant latexfiltered through cheesecloth.

The latex obtained from this reaction was milk-white in color and muchless viscous than such products obtained by prior processes.

The analytical results of this experiment are as follows:

Total Solids, 40.0 Coagulum, none Residual Monomer, 0.31 Conversion,99.2

K Value 79.0 Brookfield Vise. (cps) 14,700

EXAMPLE 2 The reaction apparatus employed in this experiment was thesame as in Example 1.

339.5 Parts of distilled water was placed in the reaction flask, 14.8parts of poly-N-vinyl-2-pyrrolidone was added thereto and the mixturewas stirred until a clear solution was obtained. Thereafter, a mixtureof 83.9 parts of N-vinyl-2-pyrrolidone and 128.5 parts of vinyl acetatewas added in one batch. The azobis-isobutyronitrile catalyst was addedin small increments as in the previous example as the remainder of theexperiment was carried out exactly as described in Example 1.

The analytical results of this experiment are as follows:

Total Solids, 39.5 Coagulum, none Residual Monomer, 0.1 1 Conversion,99.8 K Value, 77.7 Brookfield Vise. (cps) 4060 EXAMPLE 3 added theretoand the mixture was stirred until a clear solution was obtained.Thereafter, a mixture of 76.4

parts of N-vinyl-S-methyl-22 ;'rrolidone and 128.5 parts of vinylacetate was a ed in one batch. The

azobis-isobutyronitrile catalyst was added in small increments and theremainder of the experiment was carried out exactly as described inExample 1. The analytical results of this experiment are as follows:

Total Solids, 39.5 Coagulum, .0 Residual Monomer, 0.23 PresentConversion, 99.4 K Value, 79

Brookfield Viscosity 1275 V In a similar manner other copolymers of theclass described hereinabove can be employed in place of the specificreactants employed in the examples with similar results attending.

Reference in the specification and claims to parts, proportions andpercentages unless otherwise specified refer to parts, proportions andpercentages by weight.

It is obvious that numerous changes and modifications can bev made inthey above described details without departing from the spirit andnature of the invention. Therefore, it is to be understood that any suchchanges and modifications are included within the scope of the inventionand that the invention is not to r be limited except as set forth in theappended claims.

What is claimed is: 1. An emulsion copolymerization process forproducing an aqueous emulsion comprising copolymerization ofapproximately by weight 1-99 parts of an N-vinyl lactam and 99 to 1parts of a vinyl ester having the formula wherein R is C alkyl, in anaqueous medium having a total solids content by weight of about 40 to 60percent and containing as seeding agent 5-20 percent polymeric N-vinyllactam based on the amount of said N-vinyl lactam.

2. A process according to claim 1 wherein the monomers to be polymerizedare N-vinyl-2-pyrrolidone and vinyl acetate and the process is carriedout in the presence of poly-N-vinyl-2-pyrrolidone as seeding agent.

3. A process according to claim 1 wherein the monomers to be polymerizedare N-vinyl-5-methyl-2- pyrrolidone and vinyl acetate and the process iscarried out in the presence of poly-N-vinyl-2-pyrrolidone as seedingagent.

4. A process according to claim 1 wherein the reaction is carried out ata temperature of about C. to about C.

5. A process according to claim 4 wherein the reaction is carried out inthe presence of a free-radical initiator.

6. A process according to claim 4 wherein the reaction is carried out inthe presence of an inert gas.

7. A process according to claim 1 wherein said polymeric N-vinyl lactamcorresponds to a homopolymer of said monomeric N-vinyl lactam.

1. AN EMULSION COPOLYMERIZATION PROCESS FOR PRODUCING AN AQUEOUSEMULSION COMPRISING COPOLYMERIZATION OF APPROXIMATELY BY WEIGHT 1-99PARTS OF AN N-VINYL LACTAM AND 99 TO 1 PARTS OF A VINYL ESTER HAVING THEFORMULA
 2. A process according to claim 1 wherein the monomers to bepolymerized are N-vinyl-2-pyrrolidone and vinyl acetate and the processis carried out in the presence of poly-N-vinyl-2-pyrrolidone as seedingagent.
 3. A process according to claim 1 wherein the monomers to bepolymerized are N-vinyl-5-methyl-2-pyrrolidone and vinyl acetate and theprocess is carried out in the presence of poly-N-vinyl-2-pyrrolidone asseeding agent.
 4. A process according to claim 1 wherein the reaction iscarried out at a temperature of about 75* C. to about 95* C.
 5. Aprocess according to claim 4 wherein the reaction is carried out in thepresence of a free-radical initiator.
 6. A process according to claim 4wherein the reaction is carried out in the presence of an inert gas. 7.A process according to claim 1 wherein said polymeric N-vinyl lactamcorresponds to a homopolymer of said monomeric N-vinyl lactam.